The present invention relates to battery recharging circuits for recharging standard size rechargeable batteries used in wireless devices and also relates to microphones using rechargeable batteries.
The prior art contains several recharging circuits for recharging batteries in wireless devices such as cell phones, portable phones, personal data assistants, wireless microphones, etc. Many of these devices utilize standard batteries sizes such as size AAA, AA, C, D or 9-volt batteries. Both rechargeable battery types such as nickel-cadmium and nickel-metal-hydride (NiMH) type batteries and non-rechargeable battery types such as manganese-dioxide and alkaline (Alk) type batteries are available in standard battery sizes. Users are warned not to recharge the non-rechargeable battery types because attempting to recharge such non-rechargable batteries can result in leakage, overheating and/or explosion. Many of the prior art recharging circuits perform electrical tests on the batteries being recharged to determine if the batteries are a rechargeable type and if not prevent charging of non-rechargeable batteries.
In certain ranges of charged states, non-rechargeable batteries can be readily distinguished from rechargeable batteries, but in other ranges of charged states, the non-rechargable batteries cannot be distinguished readily from rechargeable batteries by the prior art recharging circuits. When a battery is in a charged state where it is difficult to distinguish rechargeable batteries from non-rechargeable batteries, the prior art generally applies a charging voltage for a short period of time and then retests the battery to determine if the battery is a rechargeable battery. The prior art testing for rechargeable batteries has deficiencies as well as running the risk of battery leakage, overheating and explosion.
In prior art wireless microphones which use standard sizes of rechargeable batteries, the batteries must be removed and placed in a separate battery charger. Battery removal and replacement runs the risk of causing damage to the microphone.